The present invention relates to a database management system and more particularly to a multi-dimensional data storing and retrieving method suitable for storing a great deal of multi-dimensional data in a memory unit with a smaller capacity required and retrieving the multi-dimensional data at a higher speed.
The multi-dimensional retrieval function for retrieving data specified by any combination of members of dimensions is one of the most fundamental functions in the multi-dimensional database management system for supporting a many-faceted analysis of data. In order to process this function at a high speed, the following technique has been used heretofore.
The system of storing data in a hard disk unit in a format suitable for retrieval of multi-dimensional data involves a system in which data are linearly arranged in order of a nest of dimension coordinates in accordance with the memory array method of array data of a computer language and stored, a system in which the multi-dimensional data space is assumed to be divided in the direct product of sub-spaces in which data having effective values are distributed in sparsely and sub-spaces in which data having effective values are distributed densely and a memory area is allotted to only sub-space of the latter sub-spaces which is not empty to be pointed by the pointer array corresponding to the former sub-space (U.S. Pat. No. 05359724), and a grid file system in which attributes of record data of a relational model are considered as dimensions and the data space constituted by the dimensions is divided into rectangular parallelepipedic blocks so that pages for storing records belonging to the same block are allotted and indexes for recording the correspondence of coordinates of the blocks and the pages are prepared (Nievergelt, J., et al., "The Grid File: An Adaptable, Symmetric Multikey File Structure", ACM Transactions on Database Systems, vol. 9, No. 1, pp. 38-71, 1984).
The data retrieval can be made at a high speed by means of the parallel processing. In order that the parallel processing is effective, it is necessary to uniform loads imposed on a plurality of processing units. In order to uniform the loads of the data retrieval, it is important how data are allotted to the plurality of processing units and are stored. The relational database management system uses the round-robin partitioning, the hash partitioning and the range partitioning methods (DeWitt, D., et al., "The Gamma Database Machine Project", IEEE Transactions on Knowledge and Data Engineering, Vol. 2, No. 1, pp. 44-63, 1990).